Tropical forests have been cut at a rapid rate to make room for agriculture and to extract their many valuable products. Every year, at least 180,000 square kilometres of tropical forests and woodlands are cleared for unsustainable shifting cultivation, settlements, ranching and other agricultural schemes. Timber harvest contracts have usually been short term and have provided little or no incentive for timber companies to replant. So little reforestation has been done in the Tropics that many people believe these forests cannot be restored. Several factors underlie the destruction of tropical forests. One is inequitable distribution of land and power, political and economic, enabling the wealthy to liquidate forests for profit; and forcing large numbers of landless and near-landless to colonize the forests and to try to farm land that is unsuitable for agriculture. Another is insecure land tenure for forest dwellers leading to short term maximization of profits. Further inequities in the international economy force lower-income countries to sell whatever they can, including their forests.
According to Holdridge's system of ecological zones, tropical rain forest has a mean annual temperature of 24 or more and an average annual rainfall of 8,000 or more mm.
The largest remaining areas of tropical rain forests are in Brazil, Congo, Indonesia, and Malaysia. Through transpiration, the enormous number of plants found in rain forests return huge amounts of water to the atmosphere, increasing humidity and rainfall, cooling the air for miles around. In addition, tropical forests replenish the air by utilizing carbon dioxide and giving off oxygen.
The world's tropical forests circle the globe in a ring around the Equator. These forests cover less than 6 percent of the Earth's land area, but they contain the vast majority of the world's plant and animal genetic resources. Forests slow the onslaught of tropical downpours, use and store vast quantities of water, and help hold the soil in place. When trees are cleared, rainfall runs off more quickly, contributing to floods and erosion. Tropical forests provide many valuable products including rubber, fruits and nuts, meat, rattan, medicinal herbs, floral greenery, lumber, firewood, and charcoal. Such forests are used by local people for subsistence hunting and fishing. They provide income and jobs for hundreds of millions of people in small, medium, and large industries.
Once covering some 15.3 billion acres (6.2 billion ha), tropical forests have been reduced through cutting and clearing by 210 million acres (85 million ha) between 1985 and 1990. Ethiopia had 45% of its original forest cover in 1900; today it has only 1-3% remaining. By 1920 Haiti had 60% of its forest left; which by 1987 was down to only 2%. Madagascar has lost 93% of its forest cover.